Localisation of sex steroid receptors and effect of Tamoxifen upon glioma cell lines in vitro

Abstract

Gliomas are the most common form of primary tumour of the central nervous system with a lethality rate approaching 80% in the first year of diagnosis. Their highly invasive nature renders local therapies such as surgery and radiation ineffective, whereas novel approaches such as immunotherapy are being actively studied as possible adjuncts in the treatment of patients with malignant gliomas. A number of factors have been proposed to play a role in glioma immune escape. These include their poor immunogenicity since they do not express specific glioma antigens; their location with in the CNS, which is considered to be an immune-privileged organ and some indications that glioma cells are capable of releasing various immunosuppressive cytokines, which inhibit the cytotoxic function of T cells. Glioma brain tumours differ from most other cancers by their diffusive invasion of the surrounding normal tissue and frequent recurrence following all forms of therapy. It is this invasive nature that ultimately contributes to their poor 6-12 month prognosis. Because of their profound devastating effect much research is currently being carried out to investigate gliomas and it seems that the chemosensitivity of gliomas, i.e. the analysis of glioma response to a specific drug, is a focal point of developing treatment, and more recently an idea of prevention. Tamoxifen is a member of the selective estrogen receptor modulator (SERM) family, is widely used in the treatment of estrogen receptor (ER)-expressing breast cancer. It has been shown that a high dose of Tamoxifen has cytotoxic activity against gliomas, but whether this effect is drug specific or represents a general property of SERMs is unknown. Tamoxifen is considered to exert its anitproliferative effect in ER-positive breast cancer neoplasms through blocking the estrogen receptor, thus, inhibiting gene transcription and cellular proliferation. In vitro studies have shown that Tamoxifen can inhibit the growth of a brain tumour cell lines, but whether the mechanism involves oestrogen blockade remains a matter of some debate. As well as its effect in blocking estrogen receptors, Tamoxifen is also known to exert antiproliferative effects via non-receptor mediated mechanisms including the blockage of Protein Kinase C, inhibition of the Mitogen-7 Activated Protein Kinase (MAPK) family among a vast array of cellular signalling pathways. This study investigated the expression of sex steroid receptors in glioma cell lines using molecular biology technique (RT-PCR), and immunological tecimique (Dot blot, and Western blot). The cells were then separated in different groups of treatment (Tamoxifen, or estradiol and a combination of the two drugs) to obtain any differences in their morphological characteristics, the COX-2 immunoreactivity levels, and the levels of saturated and unsaturated fatty acids. The results showed a molecular expression of sex steroid receptors on the glioma cells, i finding that was later confirmed employing immunological techniques. The cells later showed significant differences on the treatment groups with the most changes obtaining on the projection (length and number) of the cells. The levels of COX-2 were higher on the treatment group (Tamoxifen) indicating more chances of tumour development in later stages. Furthermore, an increase of saturated fats in comparison with the unsaturated was shown in all the groups of treatment (Tamoxifen, estradiol, and Tamoxifen plus estradiol) but with no significant differences with the control group. In conclusion, the results of this study showed an expression of Estrogen and Progesterone receptors on the glioma cell lines, as well as morphological differences with significant difference on the projection length and number of projections between the different treatments of drugs (Tamoxifen and estradiol). The tamoxifen treated cell lines showed an increased COX-2 immunoreactivity, and high levels of saturated fatty acids in comparison with the very low levels of the unsaturated fatty acids